Histological study of intraocular changes in rabbits after intravitreal gas injection.

To study the effects of different intravitreal gases on intraocular tissues, adult pigmented rabbits were given 0.4 mL intravitreal injections of air, 50% sulfur hexafluoride (SF6) and air, 100% SF6, 50% perfluoropropane (C3F8), or 100% C3F8. On postinjection days 1, 4, 7, and 14, the eyes were removed and the iris, ciliary body and retina processed for light and electron microscopy. Histopathological examination found no abnormalities in eyes that received air and none in the irises of gas-injected eyes. Eyes that received 50% or 100% SF6, or 50% C3F8 had vacuolar changes in the ciliary body and retina after maximum gas expansion; these changes were transient, returning to normal as the gas was absorbed. Eyes that received 100% C3F8 suffered irreversible damage to the ciliary body and retina, in both the superior and inferior portions. These observations indicate that expansion of some intravitreal gases can cause both reversible and irreversible changes in intraocular tissues. The degree of damage is affected by the duration of exposure and the gas concentration. Highly concentrated, long-lasting gases can cause irreversible changes resulting in breakdown of the blood-ocular barrier and impaired retinal function.

[Superoxide generated by polymorphonuclear leukocytes and retinal lipid peroxidation in uveoretinitis].

The presence of superoxide generated by polymorphonuclear leukocytes (PMNs) was demonstrated in an experimental autoimmune uveoretinitis (EAU) model. Histopathological examination of the eyes, enucleated sequentially after the onset of EAU, and determination of retinal lipid peroxidation (LPO) revealed an increase in LPO products with progressive retinal tissue damage. In addition, histopathological changes, predominantly degeneration of the retinal outer segments, and increased retinal LPO were confirmed in vitro by culturing naive neural retina with activated PMNs. This increased LPO was inhibited by superoxide dismutase (SOD). These data suggest that lipid peroxidation reaction involving superoxide may play an important role in the pathogenesis of retinal tissue damage in ocular inflammatory disease characterized by the infiltration of PMNs.

Measurement of Howship's resorption lacunae by a scanning probe microscope system.

We have developed a novel ultrastructural assay system for osteoclastic resorptive function. After osteoclasts had been co-cultured on dentine slices for 48 hr, the slices were fixed with glutaraldehyde and examined by means of backscattered electron, scanning electron, and scanning probe microscopies. Backscattered electron images showed areas of low mineralization on dentine surfaces, which, by superimposition of concave-convex images, corresponded to resorption lacunae. The measurement of such resorption lacunae by scanning probe microscopy revealed 3-dimensional topography and their exact depths and volumes. Analysis based on this system provides reliable qualitative and quantitative assessment of osteoclastic resorption.

Localization of S-antigen under various conditions of light or dark adaptation in the rabbit.

The localization of the S-antigen was studied by electron microscopy in the rabbit eye, under three conditions of adaptation: A) 24-hour dark adaptation, B) 24-hour dark adaptation and 1.5-hour light adaptation and C) light adaptation for 30 hours. The Fab' fraction of the IgG of rabbit against the swine S-antigen was labeled with horseradish peroxidase (HRP) and was used as the marking antibody. In Group A, the HRP reaction products indicating the S-antigen were found mainly in the disk and plasma membranes of the outer segments of the photoreceptor cells. The reaction products were also found diffusely in the cytoplasm of the inner segment with the exception of the mitochondria and nucleus. In Group B, the phagosomes were found surrounded by the multilayered microvilli of the retinal pigment epithelial (RPE) cells; the reaction products were scarcely found in the phagosomes but were seen in the microvilli. Some weak reaction products were also encountered in the cytoplasm of the RPE cells. In Group C, after 30-hour light adaptation, many phagosomes were found but they contained almost no reaction products. However, the microvilli of the RPE cells surrounding the phagosomes showed a fair amount of the reaction products. The cytoplasm of the RPE cells contained abundant reaction products, particularly in the area of the basal infoldings. The reaction products were also seen in the Bruch's membrane and the endothelial cells of the choriocapillaris. It was thought that the S-antigen is taken up by the RPE during phagocytosis of the shed outer segments and is transported to the choriocapillaris.